DESCRIPTION (the applicant's description verbatim): The goal of this proposal is to understand the molecular mechanisms of maladaptation in heart failure. Over the past number of years, the approach in my laboratory has been to use the mouse as a model system and combine sophisticated measures of physiological function with gene-targeting to understand mechanism of disease. The initial focus was on beta-adrenergic receptor (betaAR) function in heart failure. This proposal extends observations made over the past 4 years to novel signaling pathways involved in betaAR signaling and cell survival. The following specific aims are proposed: 1) To test the hypothesis that betaAR downregulation and chronic betaAR desensitization is maladaptive in heart failure: Transgenic mice with cardiac overexpression of wild type A-kinase anchoring proteins (AKAP) (AKAP75) and a dominant negative AKAP (AKAP45) will be characterized and then mated into 2 murine heart failure models (MLP-/- and calsequestrin overexpression). Comprehensive physiological, biochemical and molecular analysis of the phenotype will be performed. 2) To determine the molecular mechanism for the novel finding that phosphoinositide-3 kinase (PI3K) forms an intracellular complex with betaARKinase. Constitutively active and catalytic inactive mutants of P13K will be transfected into cells along with wild type or mutant beta1Ars lacking the betaARK phosphorylation sites. Comprehensive analysis of betaAR function will be performed. 3) To test the hypothesis that activation of PI3Kp110gamma in the heart in response to the stress of pressure overload provides a mechanism to counter-balance cellular signals promoting cell death. Transgenic mice overexpressing the constitutively active and catalytic inactive mutants of PI3Kp110gamma will be subjected to pressure overload. Comprehensive physiological, biochemical and morphological analysis of the phenotype with pressure overload hypertrophy will be performed. 4) To determine whether the enhancement of PI3Kp110gamma mediated signaling in experimental heart failure can prevent the progression from compensated hypertrophy to decompensated heart failure. Calsequestrin overexpressing mice will be mated to transgenic mice overexpressing the constitutively active and catalytic inactive mutants of PI3Kp110gamma followed by a comprehensive analysis of the phenotype.